Cytogenetic diagnoses after chorionic villus sampling are less reliable in very-high- or very-low-risk pregnancies

An increasing number of cytogenetic prenatal diagnoses are performed on chorionic villus samplings. The accuracy of this method is influenced by chromosomal mosaicism, mostly confined to direct preparation methods. Especially those investigators who have experienced false-negative and false-positive findings propagate the combined use of direct and culture methods. Yet large collaborative studies have shown that in approximately two-thirds of diagnostic cases only one procedure is applied. Moreover, the accuracy of a cytogenetic investigation depends not only on the ontogenetic origin of the tissues investigated, but also on interacting factors such as the ‘a priori risk’ and the ‘predictive value of a cytogenetic finding’. On this basis a differentiated prenatal diagnostic procedure is discussed, including either sole short-term culture (STC), combined STC and long-term culture (LTC), primary amniocentesis (AC), or primary percutaneous umbilical blood sampling (PUBS). The predictive value of the cytogenetic diagnosis from CVS varies significantly dependent on the a priori risk of a chromosome aberration and, in the case of an abnormal karyotype, on the specific chromosome involved. A non-mosaic and ‘non-lethal’ trisomy detected in STC is highly representative of the embryo/fetus, but there are exceptions of limited predictive value, e.g., trisomy 18. Guided by the strategy of an optional follow-up by LTC, AC, or PUBS in 1317 successive CV samplings, we are not aware of a false-negative diagnosis, but probably had one false-positive diagnosis: 47,XXY after STC; 46,XY after LTC. When referring to the rate of fetuses with an unbalanced karyotype expected in the different indication groups, a relative increase of false-positive findings in the very-low-risk group (maternal age ⩽35 years of age) and of false-negative findings in the very-high-risk group (abnormal ultrasonographic findings) of pregnant women when only performing CVS becomes obvious. Because of this dilemma, AC or—especially in the latter group—PUBS might be primarily offered to these indication groups instead of CVS.     

评估可离子化有机化合物的生物累积潜力：当前的认知和研究的重点

本研究的目的是回顾目前关于可离子化有机化合物(IOCs)的生物累积潜力的认知,重点讨论鱼类经验数据的有效性。IOCs在鱼体内的生物积累潜力可以很好地表征为：依赖pH的鳃摄取和排泄,肠道吸收和磷脂吸附(膜-水分区)。关键的挑战包括缺乏关于IOCs生物转化和血浆结合的经验数据。鱼拥有多种蛋白质,可以在细胞膜上传输IOCs。然而,除了少数情况下,这种传输对环境污染物的吸收和积累的意义是未知的。本文提出了2个研究案例。第一个描述了pH值和生物转化对有机酸和碱的生物富集的建模作用,而第二个则采用了一个更新的模型来研究导致全氟烷基酸积累的因素。全氟化烷基酸个案研究是值得关注的,因为它说明了膜转运蛋白在肾脏中可能具有的重要性,并强调了交叉比对方法(read-across approaches)的潜在价值。认识到当前需要对IOCs进行生物累积危害评估和生态风险评估,作者提供了一个分层策略,从保守的假设(模型和相关数据)到需要化学特定信息的更复杂的模型。
精选自Armitage, J. M., Erickson, R. J., Luckenbach, T., Ng, C. A., Prosser, R. S., Arnot, J. A., Schirmer, K. and Nichols, J. W. (2017), Assessing the bioaccumulation potential of ionizable organic compounds: Current knowledge and research priorities. Environmental Toxicology and Chemistry, 36: 882–897. doi: 10.1002/etc.3680
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3680/full
     

Model and input uncertainty in multi-media fate modeling: benzo[a]pyrene concentrations in Europe

This paper evaluates the contribution of (i) uncertainty in substance properties, (ii) lack of spatial variability, (iii) intermodel differences and (iv) neglecting sorption to black carbon (BC) to the uncertainty of Benzo[a]pyrene (BaP) concentrations in European air, soil and fresh water predicted by the multi-media fate model Simplebox. Uncertainty in substance properties was quantified using probabilistic modeling. The influence of spatial variability was quantified by estimating variation in predicted concentrations with three spatially explicit fate models (Impact 2002, EVn BETR and BETR Global). Intermodel differences were quantified by comparing concentration estimates of Simplebox, Impact 2002, EVn BETR and the European part of BETR Global. Finally, predictions of a BC-inclusive version of Simplebox were compared with predictions of a BC-exclusive version. For air concentrations of BaP, the lack of spatial variability in emissions was most influential. For freshwater concentrations of BaP, intermodel differences and lack of spatial variability in dimensions of fresh water bodies were the dominant sources of uncertainty. For soil, all sources of uncertainty were of comparable magnitude. Our results indicate that uncertainty in Simplebox can be as large as three orders of magnitude for BaP concentrations in the environment and would be substantially underestimated by focusing on one source of uncertainty only.     

Stoichiometry, growth, and fecundity responses to nutrient enrichment by invertebrate grazers in sub-tropical turtle grass (Thalassia testudinum) meadows

Although the effectiveness of herbivores in mitigating the effects of nutrient enrichment is well documented, few studies have examined the effects of nutrient enrichment on components of consumer fitness. Enclosures were deployed in shallow turtle grass (Thalassia testudinum) beds in Florida Bay, Florida in fall 2003, spring 2004, and fall 2004 to measure the effects of nitrogen and phosphorous enrichment on the growth, fecundity, and stoichiometry of three invertebrate epiphyte grazers commonly associated with T. testudinum. The gastropod Turbo castanea exhibited significantly greater wet weight gain and lower C:P and N:P in enriched than in ambient treatments. Although nutrient enrichment did not have any significant effects on the growth of caridean shrimp (treatment consisted of several different caridean shrimp species), their C:N was significantly lower in enriched treatments. The final size and stoichiometry of the hermit crab Paguristes tortugae was not significantly affected by nutrient enrichment, nor did nutrient enrichment significantly affect the fecundity of P. tortugae, the only grazer in which gravid individuals or egg masses were present. Our study demonstrated that nutrient enrichment of primary producers can positively affect the growth of marine invertebrate grazers and alter their stoichiometry; however, these effects were species-specific and may be dependent upon the life stage, specific diets, and/or compensatory feeding habits of the grazers.     

Spectral characteristics of plant communities from salt marshes: A case study from Chongming Dongtan, Yangtze estuary, China

The spectral reflectance of recently formed salt marshes at the mouth of the Yangtze River, which are undergoing invasion by Spartina alterniflora, were assessed to determine the potential utility of remotely sensed data in assessing future invasion and changes in species composition. Following a review of published research on remote sensing of salt marshes, 53 locations along three transects were sampled for paired data on plant species composition and spectral reflectance using a FieldSpec? Pro JR Field Portable Spectroradiometer. Spectral data were processed concerning reflectance, and the averaged reflectance values for each sample were reanalysed to correspond to a 12-waveband bandset of the Compact Airborne Spectral Imager. The spectral data were summarised using principal components analysis (PCA) and the relationships between the vegetation composition, and the PCA axes of spectral data were examined. The first PCA axis of the reflectance data showed a strong correlation with variability in near infrared reflectance and ‘brightness’, while the second axis was correlated with visible reflectance and ‘greenness’. Total vegetation cover, vegetation height, and mudflat cover were all significantly related to the first axis. The implications of this in terms of the ability of remote sensing to distinguish the various salt marsh species and in particular the invasive species S. alterniflora were discussed. Major differences in species with various physiognomies could be recognised but problems occurred in separating early colonising S. alterniflora from other species at that stage. Further work using multi-seasonal hyperspectral data might assist in solving these problems.     

Foraging patterns of yellow-bellied marmosts: role of kinship and individual variability

Summary Two colonies of yellow-bellied marmots (Marmota flaviventris) at an elevation of 2900 m in Colorado were studied to elucidate the role of various behavioral and ecological factors as determinants of spatial foraging patterns. The locations of known individuals were periodically recorded. These locality data were plotted as three-dimensional block diagrams, the peak heights representing the frequency of observation. Predation risk and vegetation distribution influenced the location of foraging areas; kinship was an important factor in the determination of the amount of foraging area shared between individual marmots. Spatial overlap tended to be greater among close kin, but this was modified by individual behavioral characteristics, reproductive state, the existence of separate burrow systems within a colony, and the age of the animal. Mothers and juveniles, and littermates as young and resident yearlings, had nearly identical foraging areas.